import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CounterServlet extends HttpServlet {

 private int counter;

 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 resp.getWriter().println("Hello visitor no. " + (++counter));
 }

}